Electron discharge storage tubes



Nov. 11, 1958 s. HANSEN ELEcTRoN DISCHARGE STORAGE TUBES 4 Sheets-Sheet l Filed April 25, 1955 Nov. 11, 1958 Filed April 25. 1955 S. HANSEN ELECTRON DISCHARGE STORAGE TUBES 4 Sheets-Sheet 2 PSD 2 5 4 5 6 7 6 9 IU V a n l c1 o a n a 5I Vu VC (7 (7 4 (7 (7 V l, 7 l,

Y 1 VB /so Vu S/EGFQ/E /Q/SEM INVENTOR.

NJW M NO V 11, 1958 s. HANSEN 2,860,282

ELECTRON DISCHARGE STORAGE TUBES Filed April 25, 1955 4 sheets-Shen 5 I Ll K G Z4 LIG l ..nu l M Nov. 11, 1958 s. HANSEN 2,360,282

ELECTRON DISCHARGE STORAGE TUBES Filed April 25, 1955 4 Sheets-Sheet 4 j' INVENTOR.

www JM United States Patent() ELECTRON DISCHARGE STORAGE TUBES Siegfried Hansen, Los Angeles, Calif., assignor to Litton Industries of California, Beverly Hills, Calif.

Application April 25, 1955, Serial No. 503,614

22 Claims. (Cl. S15-8.5)

The present invention relates to electron discharge storage tubes and more particularly to an electronic signal shifting apparatus in which binary electrical intelligence signals stored on areas of a secondary electron emissive storage surface are transported to remote areas of the storage surface by being shifted across the storage surface to the remote areas.

In the electronic computing and switching art, electron discharge storage apparatus utilizing the signal retaining properties of a secondary emissive storage surface are widely used for the storage of binary information. In the typical operation of a prior art storage tube, storage of an applied binary electrical intelligence signal is accomplished by directing an electron beam at an area of a secondary emissive target surface and modulating the beam in accordance with the applied intelligence signal in such a manner as to produce on the area either a charge pattern or a potential level representative of the intelligence signal. Interrogation or read-out at a later time of an intelligence signal stored in this manner is accomplished by again directing the electron beam at the area in which the intelligence signal has been stored and noting as the beam impinges upon the storage area the resultant modulation of the beam current or of some related quantity.

Various methods of modulating the electron beam in accordance with an applied binary intelligence signal have been utilized in the prior art for effecting storage of the intelligence signal on a Secondary emissive surface with the modulated beam. Itis advantageous to consider these methods in some detail since a general familiarity with the basic principles of operation of prior art storage tubes will greatly facilitate understanding of the novel mode of operation of the signal shifting apparatus of the present invention.

In one species of prior art storage tube, for example, a cathode which is the source of the electron beam is normally maintained at a markedly negative potential with respect to a target electrode, so that electrons striking an area of the target surface have suicient velocity to eject more electrons from the area by secondary emission than arrive in the beam, thereby causing the area to Vcharge positively with respect to the cathode because of the net loss of electrons from the area through the described secondary emission phenomena. In thisspecies of storage tube, therefore, the electron beam will write positive charge on the storage surface whenever it impinges on the surface, Modulation of the writing beam by a binary intelligence signal is accomplished by applying the intelligence signal to a grid structure to either interrupt or pass the electron beam in accordance with the binary signal as the beam is directed at a selected storage area, thereby effectively storing the binary signal on the storage area as a region selectively charged to an upper or lower range of potential. A signal storage apparatus of the described type is exemplified by the arrangement shown in U. S. Patent No. 2,689,301, entitled Arrangement for Storing Intelligence Signals Electronically, by A. M. Skellett, issued September 14, 1954.

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In the equipment shown by Skellett an ladditional cathode and beam forming apparatus is provided for forming a so-called "holding beam which Ifloods electrons over the entire storage surface to maintain or hold all storage areas at their upper or lower range of potentials so that stored or written charge does not leak oi the storage surface but is instead continuously regenerated by the action ofthe holding beam. The cathode which is utilized in the formation of the holding beam is maintained at a potential fairly close to the normal potential of the storage surface. Electrons in the holding beam therefore have relatively low velocities, their nal velocity upon impingement being selectively determined at each storage area by the potential range to which the storage area has been charged by the writing beam. The secondary electron emission ratio of a storage area bombarded by the holding beam is thereby selectively determined by the potential range of the bombarded area. If, for example, a storage area has been charged or left at a predetermined lower range of potential, the secondary emission ratio of the area will be less than one when the area is bombarded by the relatively low Velocity electrons of the holding beam, causing electrons to deposit on the storage area, thereby charging the storage area towards the potential of the holding beam cathode.

On the other hand if the storage area is already at a predetermined upper range of potential (because of action of the writing beam), then the secondary emission ratio of the area will be greater than one when the area is bombarded by the relatively low velocity electrons of the holding beam, thereby causing the area to charge positively with respect to the potential of the holding beam cathode because of the net loss of electrons through secondary emission. Thus in operation, storage areas at either the upper or lower range of potential are maintained at their respective ranges of potential by the action of the holding beam.

Another species of prior art signal storage 'apparatus which also uses a writing7 beam (a beam in which the electrons have sufficient velocity so that they uniformly cause a secondary emission ratio greater than one in a bombarded storage area) is based upon certain principles of operation first suggested by Prof. F. C. Williams of the University of Manchester, England. In this type of storage tube apparatus binary intelligence signals are not applied to a grid structure to pass and interrupt the writing beam, but are instead utilized to deflect the writing-beam after it has been directed at a selected storage area so as to draw at the storage area a charge pattern or image which is representative of the binary intelligence signal. For example, signals representing the binary digits 0 and 1 have been variously represented as dot and dash, dot and double dot, and dot and circle patterns of charge drawn at the associated storage area by the writing beam. Readout of a charge pattern of this type is :accomplished by again interrogating the area with the writing beam. Auxiliary flood type holding beams are sometimes pro.- vided with Williams tube apparatus. An excellent summary and bibliography to Williams tube apparatus may be found in an article entitled An Improved Cathode Ray Tube Storage System, by R. Thorenscn, at page 167 of the Proceedings of the Western Computer Conference,

in accordance with the applied binary intelligence signal,`

so that a storage area at which the beam is: directed will have a secondary emission ratio less than or greater than one in accordance with the applied-intelligence signal.

. In an apparatus of this type the intelligence signal is eifectively being utilized for switching the electron beam beaccomplished' b 'y rel-interrogatingjthe L n h`t 5 -tron beam in either`its` holding 'beam or phase of operation.

Because of theeitremely highffspeed electron beam may' beideflecte'dfto asel `ted 'ora a, `prior art storage tubes of thedescrlbedztype"ae'verywell 10 adapted for providing high'speed"fn`domfaccessfmemory systems for use in connection-with'electrnie; ompaters and switching systems. Indie emputsr'- rt'the term random aceess l as appliedt'o ariel tronic memory meansthat all storage locations iuftheineinory are vequal- V ly accessible, ,essentially` the sfam'e amount of Vtime being required for read out' of"biriar `y.info`r`mation'fromany selected storage location inith'e memory.

[In many types of computation a yserial electronic memory in which the storage'l'ocations in themer'n'ory "are consecutively available at al` reading's'tatio'n is preferable `to a "random access 'memory In `a 'puiely'serial eleetroniewmern'ory one gains access to a selected storage Vlocationrnerely'by'waiting for theV selected storagelocation to appearat the reading station. It is generally recognized'y by thoseH skilled in 'the Aart thatfnany fewer ,components are u tilizedforA storagefandfread out from a seriaVmenlory than from a random ,access memory l,and thereforeserial memory systems ofv'arious type'sare widely used in theelectronic'computing and lswitching arts. Serial memory systems presently utilized are essentially mechanisms 'for transporting binary ,intelligence signals from a'r'ec'ordingI or writing station to a r'emote reading station so that intelligence signals seriallyapplied at the writing Vstation are conveyed kas'aA serial signal train tothe reading ystation'bysom'e simple and completely automatic mechanism.

' lFon example, in a magnetic drum or magneticftape ff:

type'o'f .serial memory, binary'intelligence signalsfare written'or'stred on aimag'ne'tizable surface of a ytape ordrumv as bidirectionally magnetiz'edareas ofthe surface,` these stored.`signals,being transported to a remote yreading transducer by` moving the tape or` drum soas to Vpass the magnetized arealsgbeneaththe reading transducer. As another eXarn'plejin affmerc'ury' delay line type of serial memory, b'inary intelligence "signals lare introduced as compressional waves a'tone end of a tube of mercury or other dense material, these compressional wave propagating .down the tube to'a reading' .trans'ducer at the remote en d of the tube. In aniag'n'etic corel shift register, binary signals are stored by'being applied to selectively magnetize an input magneticcoreof ,a serially connected chain' of cores, the magnetic state of 'each' core in thechain being transferredor shifted to the successive core at each application ,of a separatelysupplied' advancing signal, therebycausing the binarysignalsl tofbeshifted from .output core.

It-is clear that, eachv of thev'abovefdescr'ibed types lof priorsart serial memory is "based, upon afdierentfundamental method or mechanism for" transportin'gfstored binary intelligence signals; In a magnetic tape -orimagnetic drumy memory, f,r ansport ofv4 intelligence signals, is accomplished by a physical translationof'thesurface `on 'which the signals are stored. In acoustic"v memories, the fundamental vsignal ytransport mechanism is the acoustic propagation of high frequency -waves 'in a dense medium, 'In a magnetic vcorefshift register, eachcoe acts as a binary switch which, passesorblocksgan applied advancing y signalfso as to"s`e'l ectively.magnetize or notV magnetize each successive core, in'accordance with the state -of magnetization of'thepreceding 'core, fbinary intelligence -signals' being transferred ortansprted 'from core tocoreinthismanner. 'according te the, basic-geneest ef, thepresent invention there' isprovidedanew,fundamentalmethodaniapparav 75 1 -area to a remote outputarea is accomplished by cyelicallyy Y j the provision of a charge removing mechanism;trail'sf'of,

tus for transporting binary intelligence signals. Inthe l`prl'ietic'e'of'themethod of the' present invention, binary' electrical intelligence signals stored on areas of a sec-,f ondary electron emissive storage surface of a semiconduc-- tive target electrode are transported to remote areas of the storage surface by being shifted across the storage'- surface to the remote areas.

Binary electrical intelligence signals are stored on thef secondary velectron emissive storage -surface as areasl which areselectively charged to either an upper or lower. range ofl potential. Follovwing a convention commonly. used in the storage tube art signals stored as region charged tothe upper range of potential arecalled-positive-- signals while signals stored as regions charged to the lower range of potential are called negative signals.

The method of transporting a binary intelligence signal of either polarity across a storage surface comprises thej steps of first directing a narrowbeam of Velectrons atan initial area ofthe surface in which 1 the signalhas beenstored to maintain the areaat its potential range, through f a holding beam type of ac tion,so l ong as theelectron beampimp'inges upon thenareaiandlthen. deliectingth electron beam ,across thefstorage vsurfaceatapredeterv mined velocity such' that as the electron beam moves across the storagesurface, Atheregion of the storage surface beneath'the beam is maintained at the range ofpo-` tential which formerly eXiSted-atthe initial area. I n this? manner the binary signaloriginally stored -on the initial area is shiftedvby the electron beam across the storagef surface to remote areas ,of the storage surface.

In one simple embodimentpf the inventionfunidirection-9 al transport of binary signals from an .initial input storage ,deectingan electron beamy backand -forthbetweenthe f initial area and the remotearea. The'bearn is advanced from theinitial area tothenremoteyarea at tliepredeter-V i vmined velocity s o as to transport applied signals tothe' remote area at each advancingsweep of vthe beam'while on its return sweeps the beam is swept baclg tothe,. ir 1itial .area at a sufficiently higher velocity so-that. t 'ransported signals are not returned to the :initial 'area on these return sweeps but are in steadileft at theremotearea to#` which they have been advanced. In this mannersucf .cessively applied signals are unidirectionallytransported across the storage surfaceffromthe initial area to therefmote area by the corresponding advancing sweepof the electron beam. f Areas which are left behind the-bearnasg-it advances across the storage surface decay rapidly/ to vthe lower range of potential by reason of leakage throughthe semi.y conductive target electrode to a conductive backing plate which is maintained at the lower range of potential. ,Es-

sentially the use of semiconductive materialin the target electrode and the provision of a conductive backing plate atthe. lower range .of potential establishes a mecha-f nism for removing charge from the storage surfacejso that vareas of the surfacewhen chargedetothe. u pperrange of potential will be rapidly dischargedtothe lower range of potential, thereby tending to maintain the storage surface at the lower range. of potential. On them other hand, the electron beam, through its holding beam jaction, is able to maintain regions upon which it impingesat either `the lower or higher ranges of potential, thereby. overcoming at the electron bombarded regions 'thenormalftendeney of the chargeremoving mechanism to return vall surface areas to the lower range of potential, In the absence of this charge removing mechanism, transport Iof a primary sign a l across` the storage surface would result in a lineofsignal being drawnacross the' surface, the elements of the line ofsignal being remanent signals left trailing behind by the primary signal -as it- ,is transported across the storage' surface.l -I Iowever,^withf remanentgsignalE tare-effectively: erased by beings-uniformly. returned to the loweri rangerof :potentialg thereby. confiar`-V` ing transported signal to the surface region beneath `the associated electron beam. Such confinement of signals to the regions beneath their associated electron beams is a preferred mode of operation for the signal shifting apparatusnof the present invention. With this mode of operation, successive signals being shifted in a particular path across a storage surface always find the surface in a uniform condition, thereby allowing more reliable shifting of signals at higher speeds than are obtainable with other modes of operation wherein remanent signals may be encountered by an advancing primary signal.

In more complex embodiments of the present invention multiple electron beams are utilized and arrangements are made in which signals advanced by one beam are engaged by a successive beam and advanced still further, the binary signals thereby serially progressing in this manner from each beam to the successive beam at each cycle of deflection of the multiple electron beams. Very large numbers of signals may simultaneously progress in serial fashion across a storage surface in a multiple beam apparatus of this type and therefore such apparatus is well adapted for use as a serial electronic memory having relatively large signal storage capacity.

In one form of multiple beam signal shifting apparatus electrostatic deflection is utilized for simultaneously sweeping a plurality of electron beams back and forth in their advancing and return sweeps. The electron beams pass through an array of alternately connected electrostatic deflection plates and are thereby swept back and forth in synchronism by a sawtooth deflection voltage applied to the plates by a source of deflection signals. The amplitude of motion of each beam across the storage surface is equal to the spacing of the beams at the storage surface, so that every signal progressing across the storage surface is shifted a distance equal to a beam spacing at each advancing sweep of the beams, the signals progressing in this manner from beam to beam as they are shifted across the storage surface from an input storage area to a` remote output storage area. v

In a preferred embodiment of the present invention which utilizes magnetic deflection, symmetrical deflection of multiple electron beams in the described manner is more readily obtained by utilizing a signal shifting tube in which arcuate electron beams are formed which issue from a central cylindrical cathode and are directed at associated serially adjacent areas on the surface of a coaxial cylindrical target electrode which encloses the central cathode.V Initial curvature and symmetrical deflection of the beam is obtained by applying an axial magnetic field which permeates the entire structure and is cyclically varied between upper and lower values so as to correspondingly increase and decrease the curvature of the electron beams, thereby sweeping each beam forward and back between its associated area and the serially successive area at each cycle of variation of the axial magnetic field. A binary signal introduced at a selected input area will therefore be shifted around the storage surface from area to area as the electron Abeams areswept back and forth in synchronism by the cyclically varying magnetic field.

In a modified embodiment of the invention, the signal storing `capacity of the preferred embodiment of the invention is increased by many orders of magnitude by substituting a modified target electrode on which a helical conductive stripe is imprinted on the cylindrical target surface and is maintained at a relatively low potential, the successive turns of the helical stripe defining boundaries for a long helical track of unobstructed storage surface along which progressing binary signals are shifted as they are transported from an inputarea at the beginning of the track, to an output area at the end of the track. In operation, signals being shifted along the track cannot propagate across the bounding turns of the helical stripe. Thus the influence of a signal on one turn of the track is entirely isolated from adjacent turns. Because of this effect, a vertically-extended electron beam can simultaneously advance independent signals on each turn of the helical track. The number of signals which may be stored in a serial memory of this type can therefore be approximately equal to the product of the number of turns and the number of extended electron beams formed. Since intelligence signals will propagate along a quite narrow helical track, the track may have avery large number of turns packed into a target surface of relatively small total area, thereby allowing storage of a very large number of signals on the helical track. Storage capacities of thousands of signals maybe obtained in this manner on a storage surface of relatively small area.

Although conductive striping of the storage surface is a preferred modification Afor increasing the storage capacity of the signal shifting apparatus of the present invention similar results may be obtained with an unstriped target surface, by using a modified cylindrical collector in which beam forming apertures are helically arranged so that a helical array of electron beams is formed by electrons passing through these apertures. In a modified signal shifting apparatus of this type, an input terminal may be positioned at an area of the surface upon which a first beam in the helical array of beams may impinge, While an output terminal may be positioned at an area of the storage surface upon which the last beam in the helical array of beams may impinge. In operation intelligence signals applied tothe input .terminal will be serially shifted in a helical path on the storage surface from the input terminal to the output terminal, the progressing intelligence signals being shifted from beam to "beam of the helical array during the course of its passage.

It is therefore an object of the present invention to provide a method and apparatus for shifting electrical binary intelligence signals across a secondary electron emissive storage surface of a semiconductive target electrode.

It is another object of the present invention to provide an electron discharge signal shifting apparatus in which binary electrical intelligence signals stored on areas of a secondary electron emissive storage surface of a semiconductive target electrode are transported to remote areas by being shifted across the storage surface to the remote areas.

Another object of the invention is to provide a method and apparatus for transporting a stored binary electrical intelligence signal across a secondary emissive storage surface by engaging the area of the storage surface in which the signal has been stored with an electron beam and deflecting the electron beam across the surface so as to effectively shift the intelligence signal across the surface under the moving electron beam.

It is yet another object of the present invention to provide apparatus for storing electrical intelligence signals on a secondary emissive storage surface of a semiconductive target as areas selectively charged to either a lower or upper range of potential and for shifting the stored signals across the storage surface by engaging the charged areas with electron beams and deflecting the electron beams across the surface so as to shift the signals across the surface as charged surface regions maintained be neath the moving electro'n beams.

It is still another object of the present 'invention to provide apparatus for storing primary electrical binary signals on a secondary emissive storage surface of a semi conductive target as areas selectively charged to either a lower or upper range'of potential and for shifting the stored signals across the storage surface by engaging the charged areas with electron beams and ydeflecting the electron beams across the surface so as to shift the primary signals across the surface as charged surface regions main tained beneath the moving electron beams, said apparatus including mechanism for removing charge from the surface so that regions of the surface charged to the upper range of potential tend to be rapidly discharged to the lower range ofpotential unless maintained at the upper 'f7 range ofpotential by j engagement 'with electron beams, whereby primarysignals'ibeing'shiftedfacross the surface "are 'c'onnedf tofthfe surf-ace regionsbeneathj the.' moving "electron beams'while rema'nent'signalsleft' trailing behind the shifted primary signals israpidly erased by the 'charge :removing mechanism, i

' It is still 1anotherlobjectljofj'the ^inventionto"`provide a method Aand'v apparatus L'for' shifting,l ac'r'oss affs'econdary erni'ssive storage l"surface," i binary *electrical intelligence Vsignals whichliavef been stored on the surface as `areas of thesrface"selectively'charged toxeither alower or upperA range of 4ipotential;"wherein associated "electron beams are directed'atthe"chargedlareas' `to maintaineach area: at its rangeoffpotential; and"y vth'ese electronf beams are" d'ee'ctedr acrossethe'storag"surface Y'at a predeterjmined velocity sof'tht asltle'ielect'ronibe'ams' move across the :storage surfacertheiregions'f th'e 'sto'rage surface benea'th Lthe beams are v'I'naintained at" the ranges of potential 'which lforrnerly 'existed 'at' the ass'o'ciated charged areas.

It is yet another object ofthe invention to'provide a method and -apparatus for -unidir'ectionally shifting Vapplied binary electrical signals' across a 'secondary emissive storage surface frorn'a'n initial storage area` of the surface to an adjacent area by-cy'clically deflecting an electron beam back and frthbe'twee the initial area and the adjacent area. Itis 'a further bbject of vthe invention to provide Aa method 'and apparatus forunidirectionally shifting applied binary electrical signals`across a secondary emis sive'storage surface'"from aninitial storage area of the surface to an adjacent area lby cyclically -deflecting an electron beam back-and forthv across the storage surface between theinitialarea' and 'the adjacent area, the 4beam being advanced from theinitial area to the'adjacent area at a predetermined Vvelcitytso as to shiftappl-ied signals across vthe surface tofthe'adjacentarea at each advancing sweep ofthe beamg. and being swept back to the initial area at suticiently higher velo/city softhat transported signals are not returned bythe beam but are instead yleft at the adjacenty area to' which-theyrhave been advanced.

It isfstill a further :object ofthe invention to provide a signal shifting apparatus in: which a plurality of serially arranged electron beams are cyclically deflected "back and forth across a secondary emissive storage" surface, the amplitude of motion of each beam `across the storage surface being equal to the spacing of the beams at the storage surface so that binary electrical signals advanced across the surface by one beam are engaged by the successive beam and advanced'still further, the signalsl being shifted a distance equal to a beam spacing at each cycle I of deflection of the beams and thereby progressing serially in this manner from beam to 'beam as they'arefshifted across the storage surface.

It is still another objectof -the present invention to provide an electron discharge signal shifting vapparatus in which a plurality of arcuate electron beams are formed, issuing from a central'cathode-and directed at associated serially adjacent areas on a'secondary Vemissive'sto'rage surface ofl a generally cylindrical targetvelectrode which encloses the central cathode, initial curvature Vof the beams being caused by an applied magnetic field which is cyclically varied between upper and lower values so as to correspondingly increase 'and decrease the curvature of the electron 'ibeams to thereby sweep each 'beam back and forth between its associatedarea' and the vserially successive area at eachA cycle of variation of the magnetic field, -whereby binary signals `introduced at an 'input area are shifted by the electron beams from area to area as theV electron 'beams are swept `back andfforth Vby the' cyclically varying magneticield.

.It is an. additional' object of the present invention to provide-a signalgshifting apparatus infwhich a1 single extended electron beam may simultaneously shift a pluing apparatusshown in Fig. ll eachV applied binary in.V

adoptedv in referring to theseisignals; that:signails storecijV or represented as regions at the upper range of potential rality `vof'independent1'binary electrical 'signals 'ac'r o`ssf"`a secondary 'emissive 'storage surface at each advancing; sweep of the "electron beam, said apparatusvinclding. conductiveistriping'jtraversing the storage surface fat'V le'vels 'corresponding to""predeterrnined levels of' thefexp-YV tended" electro'nb'earn' and'lmaintained at a"predeterrnie`d poten'tialtoelectricallyisolate the levels of thestoag surface fromeach"other,"so that electrical 'signals bein'gj shiftedacross the storage surface at' one' levelV by "the electron beam Vcannot propagate across the striping toy adjacent levels"thereby"'permitting other Aindependen signals to'be"`shiftetljby*the"electron beamV on'Y theta'djacent levels.V Y y f The 'novell features'which are believed' tor be character istic :of the invention,bothV as toits organizatiomad method of'operationytogetherwith further objects'a'rd advantages thereof,"will' be' better understood' from .the following descriptioncsideredin connectioniwith the accompanying drawiigs'inwhich several embodiment of 'the'in'ventio'n'are illustrated by way of exampleiltr is` to beeX'pressl'y understood,A however,` that the drawing are'forth'e purposer of illustration and description joril'y and are not intended as 'a"'denition of the limitsofthe invention. p y

Fig. 1 is a schematic'diagramA illustrating a sirnplee'in` bo'diinent ofan electron dischargesignal shifting apparatus according 'tothe present invention;

Fig.l 2 is va graph which illustrates the "relationship `be tween Vthe sec'ndary emission 'ratio o'f`an electrn brn-v barde'd area of 'a secondary emis'sive storage surface iid thel Voltage potential ofthe area withv respect to the'el'e'ctron source; Y n j 'Fig 3 is a waveform v'chart illustrating on a common time`4 scale vlt'age' waveforms of electrical Asignals` -A duced inthe operationof a signal'shifting apparatusaccordin'g tothe present invention;

Fig. 4` is a schematic diagram Villustrating van Aeinbo'lif` nient of"the electron discharge signal shiftingapplrtus ofthe present invention in which a pIuralityofQeIectrn beams are utilized for serially shifting'binaryelectrical signals across'asecondary emissive storage surface' of a semiconductive target electrode; j j

.Fig-5 is an isometric view illustrating a preferredemfe bodimentof av signal'shifting apparatus according to lthe present invention; Y

Fig. 6 is a plan View of the signal shifting .apparatus shown` in Fig. 5;

Fig. 7a is'an isometric View of a modified target, electrode which may be substituted inthe preferred embodi? ment of the-signal shifting apparatus of thepresent in-` vention shown in Fig. 5 to greatly increase the signal storing capacity of the apparatus;

Fig. 7b is a-diagram showinga plane development `of a'signal storing surface of the modified target electroder shownk in Fig. 7a; and Y Y n Y Fig. 8 is an isometric view 'of' anotherlmodiedeform of the preferred signal shiftingapparatusshown ini-Fig.Y 5;'.

Referring now to Fig. `1 there is -shown an electron discharge signal shifting apparatus, according toftheinl vention, which is adapted for receiving electrical binary intelligence signals appliedv to' an input' conductor 1-2'and-, for shifting the intelligence signals to an -outputconfv ductor 13. In the internal operations of the signal shift.v

telligence signal'isfutilizedto`selectively charge anfin-l put storage area al of a secondary-emissive storagefsur" face S to either'fa4 predetermined upper range of potential` or a predetermined lower range 'of potential there, by storing the vbinary intelligence signal on thestor. age area 1I ofy surface'fS, the storedsignal-then beingv shifted or` transported across storage surface S to an out put storage area a0 which'is electricallycoupled toi out putcondu'ctor 13. The following nomenclature/)Will-be will be called positive signals, while signals stored or represented as regions at the lower range of potential will be called negative signals. As will be shown hereinafter embodiments of the present invention may be constructed in which additional intelligence signals may be applied to the signal shifting apparatus while precedingly applied signals are still being transported across the storage surface, to thereby form a serial train of intelligence signals progressing in serial order across the Storage surface between the input storage area and the output storage area. In this manner large numbers Vof intelligence signals may be simultaneously stored on the storage surface. A However, it is believed that a clear understanding of the basic Vprinciples of the invention may best be gained by considering rst the very simple embodiment of the invention, shown in Fig. l, which is adapted for the storage of a single intelligence signal rather than a plurality of intelligence signals.

As shown in Fig. 1, this simple embodiment of thev invention includes an evacuated tube or chamber E in which is provided apparatus for producing an electron beam L1 and for directing the beam at the surface S of a semiconductive target 14. Apparatus is also provided for deliecting the electron beam L1 so as to cyclically move the beam back and forth between the storage areas a1 and a0 of storage surface S.

To assist in forming electron beam L1, an electron emissive cathode K connected to a source of relatively low potential VK is provided to act as a source of electrons, electrons emitted by cathode K being attracted by an accelerating anode A which is maintained at a relatively high potential with respect to the potential VK of cathode K. Accelerating anode A has a hole or aperture h1 and is positioned with respect to cathode K so that a portion of the attracted electrons pass through aperture h1 to form electron beam L1. A pair of electrostatic deection plates D1 and D2, connected to a source of deflection signals 16, are positioned on either side of the path of electron beam L1 for Operation in deecting the beam so as to play back and forth between storage areas a1 and a0 of storage surface S. In Fig. l, beam L1 is shown as impinging upon storage area a1 while a dotted line 20 indicatesthe path beam L1 will have when it is deflected to impinge upon storagearea a0. A collector anode C, which is maintained at a relatively high potential VC, is positioned adjacent storage surface S for collecting secondary electrons which may be emittedby storage surface S when under bombardment by electron beam L1. Accelerating anode A may also be conveniently connected to the source of potential VC, as shown in Fig. l.

A grid G is provided for use in regulating the flow of electrons from cathode K to thereby control the intensity of electron current in electron beam L1. As shown in Fig. l grid G partly surrounds cathode K, grid G being connected to a source of potential VG which may be at a potential level slightly below potential VK. The rear surface of semiconductive target 14 is electrically connected to a conductive back plate B which may conveniently be a metallic film deposited on the rear surface of target 14.

As shown in Fig. l back plate B may be connected to a4 source of potential VB which is in the lower range of potential and may be at or near the cathode potential VK. Referring again tol Fig. l an output terminal O is provided electrically coupled to the output storage area a0. Output terminal O may be an isolated conductive backing or metal film on the rear surface of target 14, positioned opposite'storage area a0, as shown in Fig. l, so that intelligence signals shifted to storage area ao are capacitatively applied to output terminal O. As explained hereinbefore, input signals for the shifting apparatus are applied over input conductor 12, the signals being shown in Fig. l as originating from a source of input signals 18.

Input conductor 12 is connected to an input terminal I which is electrically coupled to input storage area a1, each applied intelligence signal thereby charging storage area a1 to a high or low range of potential in accordance with the voltage level of the applied intelligence signal. As shown in Fig. l, input terminal I is a thin conductive film coated over a portion of storage area a1.. It will-be understood that storage area a1 includes that portion of surface S which is underneath terminal I and also includes those peripheral regions of surface S surrounding terminal I which are directly charged to a high or low potential range by intelligence signals applied to input terminal I. Storage surface S ordinarily tends to be maintained at the back plate potential VB by reason of volume conduction through the semiconductive target 14 to the back plate. However, if an area of storage surface S is first charged to either the lower or upper range of potential and is then bombarded by electron beam L1 the bornbarded area will not return to the baclf` plate potential VB but will be charged by beam L1 toward one of two stable potentials corresponding respectively to the collector potential VC or the cathode potential VK `in accordance with the initial potential range of the area before bombardment. Those skilled in the art will readily' understand the mechanism by which an area of storage surface S may be charged to these alternate potential levels.

If, when an electron beam impinges on a storage area, the storage area is already at the predetermined upper range of potential then the electrons arriving at the area acquire sufficient velocity so that more electrons are ejected from the area by secondary emission than arrive at the area in the electron beam. The ejected or secondarily emitted electrons are attracted to collector anode C and are thereby removed from the bombarded area. As a result the area of storage surface S under bombardment becomes more positive by reason of the loss of the second' arily emitted electrons. Additional electrons arriving at the bombarded area will therefore have even higher velocities of impingement. The area under bombardment thus becomes increasingly positive until it is charged toA a limiting potential corresponding to the collector potential VC. i

On the other hand if the area of storage surface S is at the predetermined lower range of potential before bombardment, then electrons directed at the area in the bombarding electron beam L, will have considerably lower velocities as they arrive at the storage area so that fewer electrons are ejected by secondary emission than arrive at the storage area in the electron beam, causing a net increase or deposition of electrons on the storage area. Under these conditions the storage area rapidly charges to a potential corresponding to the potential VK of cathode K which is the source of electrons.

Thus it is clear that when under bombardment by electron beam L1 an area of storage surface S will be charged either towards potential VC or potential VK depending upon whether the area was at the predetermined upper range of potential or at the lower range of potential immediately before being bombarded by electron beam L1. Electron beam L1 therefore functions as a holding beam which maintains any area upon which it impinges at the potential range the area had before bombardment. It is also clear that if electron beam L1 is removed from such an area the area will be uniformly returned or discharged to the lower range of potential by conduction through semiconductive target 14 to back plate B.

Moreover it is a feature of the present invention thatv if beam L1 is deflected away from such an area at a sufficiently low predetermined velocity, then as the beam moves across the surface away from the area, the region of the surface immediately beneath the moving beam will be maintained at the same range of potential that originally existed at the initial area from which the beam at the'uplper range of potential.

V'present invention vthat signal Atrails of this sort are rapidly started-its"advance. 'In vthis manner ra positive or negative signal stored on storage surface S as an initial area selectively-charged to'either the upper or lowerpotential range, may be shifted across surfaceS'by electron" beam L1'as a correspondingly charged region maintained'beneath the moving electron beam.

Consider for example,referring again'to Fig. 1,'the operation' which occurs 'when electronY beam L1 is 'de'ected across vstorage surface S fromstorage area a1 to storage areaaox, Let it'be assumed in the following 'description of operation that a positive intelligence signal has been applied'to input terminal I and 'that-therefore storage area a1 has been charged to the upperv range of potential.

Y In 'operation electron beam-L1 is directed at storage'area a1 while the area is at this upper range 'of potential and is then advanced or deflected from storage area a1 to storage area a0.

As the beam in its'advance begins to move off input terminal I the beam encounters and bombards a peripheral region of storage area a1 which'has'bcome'charged by' direct conduction4 and other effects to the upper range of potential. Under bombardment by the electron stream this peripheral region rapidly becomes'more positive as itcharges because of the bombardment towards collector potential VC. 'Meanwhile as this peripheral region becomes highly charged electron beam L1 continues toad-v vance soY that this formerly peripheral region becomes .the central region Linder bombardment by the beam while furtherl peripheral regions in the direction of the advancirig beam now become charged by direction conduction and other' eifects to the upper range of potential.

' Thus when beam L1 is advanced across storage surface S from area r1-to area :zo it always encounters in the direction of its advance peripheral regions which have already become charged to the upper range of potential so long as the beam is advanced across the surface at a sufficiently low velocity which does not exceed the rate or velocity of creation of such peripherally charged region. Under these conditions,v the beam through its holding" action is able to continuously maintain a charged Vregion beneath it as it sweeps across the surface, the potential range of the region beneath the beam corresponding to the potential range of initial area a1 from which the beam started its sweep. In this manner positive signals introducedV at storage area a1 are shifted across lthe'storage surface by electro-n beam L1 as positive signal regions which are maintained beneath beam L1 as it moves across storage surface S. When such a positive signal region reaches output area a a large positive pulse is capacitivelyfcoupledKV to output terminal O and in this'fashion the shifted positive signalis applied to output terminal 13.'

' It is clear that negative signals applied to input terminal I will be similarly shifted by electron beam L1 across storage surface S to output storage area no. When a negative signal is applied to input terminal I, storage area a1 is charged to the lower range of potential and therefore when electron beam L1 is deflected from` storage area a1 to area a0 the regions beneath the moving beamv are maintained at the lower range of potential corresponding to the potential Vrange of storage area a1 fromV which the beam started its sweep. Electron beam L1 is therefore-effective in transporting negativefsignals as well as positive signals across storage surface S from input storage. area a1 toY output storage area a0.

It will be noted thatwhen a positive signal is shifted across the storage area it tends in its Vtraverse to leave remanentlyy chargedl regions trailing behind it .which are It is a feature of theA erased or discharged to the lower range of potential-byV reason oflconduction through setniconduc'tive target`14 tolitherlpotential VB of backplate B. Because offthisl effecttransported for shifted `sig-nalsare -connednfto-thef75 tarea in which a positive or negative signal has beenY surface region-beneath beamvL1. Suchconnementbf Y' shifted signals -to the region' lying beneath velectronbeanfn L1 is a preferred mode of operation'for the signal sh'ifting apparatus .of the present invention. With this mode of operation successive signals being shifted across 'the storage surface .alwaysnd the surface in a uniforrnc'on(k dition'thereby 'allowing more reliable shifting Ofsignals at higher speeds than'are obtainable with other modesof operationA wherein' remanent signal may be encountered by an advancing binary intelligence signal.

It will be remembered that vin operation vbeamfL1 'is` cyclically .swept 'back and forth between storage l areasv fai. and a0 so as toserially 'shift to area ao binary intelli gence` signals which are successively introduced at storage area a1. Unidirectional shifting'or transport of binary sigf nals in this manner is accomplished by utilizing afhighvief` locity return sweep or flyback'of beam L1 from areaao toVV ka1 so that binary intelligence signals shifted along bye-the beam on` its forward sweep will be'left at area a0 and will not be swept back again on the return sweep or. flyback. Thus in operation the described apparatus func-k tions as a single digit binary shift register in which binaryv intelligence signals are advanced in one direction bythey forward sweeps of velectron beam L1 andare left un disturbed during return sweeps of beam L1. The described method .and apparatus for shifting-in` telligence 'signals across a semiconductive secondarilyI ejmissive'storage surface may be further clarifiedy bycon siderati'on of Fig. 2 which is a conventional and remark ably, illustrative diagram which is descriptive of fthe re lationship between the potential of a storage area of surf face'S when underbombardment by electron `beam`L1 andthez secondary emissionfratio R'of electrons leaving` the bombarded storage area to the electrons .arriving-at thestorage area in the velectron beamL1.y As shown in Fig. 2 the ratio'R is plotted. on a vertical scale while the potenial' f thestorage area under bombardment .is plotted yon a horizontal scale. A dotted line 21 has .beenl drawn to indicate the transition between operating regions above dotted line 21 where` ratio R is greater than-one and operating regions below the dotted line where ratio;` R is less than one. 1, As shown in Fig. 2 thestorage area under bombard-j ment may be at an operating point at which ratiorR'is exactlyv one .and vthe region is at a predeterminedv poe. tential VR. ,This operating point,'however,is quite-u stable since the slightest increase in potential will cauu 1 the storage'area to have a ratio greater than one therebyv causing the storage area to rapidly charge towards the collector potential VC. On 4the other hand a slight de V crease in lpotential would cause the ratio R to 'drop-` below one, thereby causing the storage area underv bom-1 bardment to charge rapidly towards the cathode potential;- VK. `Thus it may beV understood that the possible po-v tentials of avstorage area under bombardment maygbe divided into a predetermined upper range of potential above potential VR and a predetermined lower range of potential below potentialVR. It is clear in-view of the foregoing that a storage area.- under bombardment will charge towards collectorfpo?" tential Vc or cathode potential VK in accordance with the range the range of potential at which the storageparezr is maintained before bombardment.` In this :manner anV stored is maintained at its 4corresponding potentialv rangeg when *bombardedl byv anelectronlbeam of the describedV type. An -area under directzbombardment by electronV beam L1 will, itis clear, tend to be either ata potential close to VC or at a potential close to VK. A positivesignalfstoredas a region of a storage area `which is at a potential; close?. to'VC` will be-surrounded because of surface conductioVV and 'otherefle'cts lby .a peripheral region which `is 'also a the upper range of potential albeit at a somewhatlower -13 potential level. Therefore as electron beam L1 is moved into this peripheral or boundary region it is able to positively charge the boundary region towards collector potential VC and is therefore able to sweep or transport a charged region beneath itself, as the beam sweeps across the storage surface. In this manner positive signals are transported across a storage surface by the electron beam. Meanwhile areas which are left behind beam L1 rapidly discharge towards the back plate potential VB thereby erasing any remanent signal which may be left trailing behind the transported signal. Y

Negative signals, which it will be remembered are represented as regions at the lower range of potential, are transported across the storage surface by a somewhat simi-1 lar mechanism. When a negative signal region is engaged by electron beam L1 the region charges rapidly towards the cathode potential VK which is in the lower range of potential. As the beam is swept forward it falls upon peripheral regions which are also at the lower range of potential both because of surface conduction in the manner described before and also because of the natural decay of any obstructing remanently charged areas by reason of leakage through the semiconductive target to the back plate. Thus as the beam is swept across the storage surface, regions beneath the beam are readily charged towards potential VK, and in this manner the negative signal is advanced across the storage surface.

When beam L1 after it has advanced a signal on its forward sweep is swept back on its return sweep with suflicient rapidity, the beam is unable to supply enough current to charge the sizable capacitances made by storage surface S and back plate B at a rate consonant with the speed of return of the beam. Therefore if the return sweep is made sutliciently rapid, the advanced signal will not be swept back again but willrbe left at the storage area to which it has been shifted.

It will be shown at a later point in this specification that a signal advanced in this manner may be engaged by another electron beam and be advanced still further.

However, confining ourselves for the moment to the consideration of the single beam shifting apparatus shown in Fig. 1, reference is made to Fig. 3 in which are illustrated on a common time scale certain signal waveforms illustrative of the operation o f the signal shifting apparatus shown in Fig. 1. Referring now to Fig. 3 there is shown a sawtooth voltage waveform S11 which may be applied to deflection plate D2 by source of deflection signals 16 to control the defiecting of electron beam L1 in the manner described hereinbefore, each extended ramp-like rise of signal Sd corresponding to the forward sweep of electron beam L1 from area a1 to area ao and each sharp fall of waveform Sd corresponding to the yback or return sweep` of beam L1 to area a1. The return sweeps of beam L1 will therefore correspond to equi-spaced time positions t1, t2, t3, as shown in Fig. 3.

For the purpose of clarifying the operation of the signal shifting apparatus shown in Fig. 1 there is also shown in Fig. 3 an input signal S1 which may be applied to input terminal I by source of input signals 18, signals S1 being composed of intelligence signals which are successively representative of ten binary digits 0011001000, these intelligence signals of signals S1 being numbered 1 through l as shown in Fig. 3. As shown in Fig. 3 the first binary digit (0) is represented by signals S1 being at arelatively low level at time t1. All other 0 binary digits are similarly represented by signal S1 being at its low level while binary 1 digits are represented by signal S1 being at its high level. For example, .the third binary digit, a binary 1 is represented by signal S1 being at its high level at time t3. Thus signal S1 at each of the times t1, t2, t3, r11, may be used to charge storage area a1 to a range of potential corresponding to the respectively associated binary digits 0011001000.

For example, at time t1, as beam L1 sweeps back to storage area a1 it finds storage area a1 maintained by signal S1 at the lower range of potential representative of the first binary digit (0). Beam L1 thereupon begins to charge area a1 towards the cathode potential VK and during the interval between times t1 and t2, as the beam moves towards storage area a1, the beam continues to charge the surface regions beneath it towards potential VK.

In this connection it is instructive to examine the waveform of an output signal SO which is produced at storage area a0 by the successive arrivals of beam L1 at storage area a0 in response to successive cycles of deflection signal S11. By considering'signal SO as shown in Fig. 3, it becomes clear that as beam L1 approaches storage area a0, shortly before time t2, storage area a0 which has been at back plate potential VB is more or less abruptly charged towards the cathode potential VK thus producing a negative voltage excursion of signal S0 which reaches its peak at time t2 as beam L1 is centered directly upon area a0. Then as beam L1 is abruptly swept back to storage area a1 the voltage level of signal SO decays again on an extended decay curve and towards back plate potential VB making another excursion towards potential VK and reaching its peak only when beam L1 again arrives at area a0 at time t3. During the time interval between t3 and t4 the voltage level of signal' SO again decays towards potential level VB until shortly before time t4 when beam L1 again reaches area a0.

However, at this time t4 the arriving electron beam L1 is shifting a positive signal region across the storage area, this positive signal region having been picked up by the beam at storage area a1 at the preceding time: t3. Thus as the advancing beam reaches storage area a0, the positive signal region is swept or shifted into storage area a0 in the manner hereinbefore described charging area a0 abruptly towards potential VC, as illustrated by the peak attained by signal SO at time t4.

Once again during the interval between t1 and t5 the voltage level of signal SO decays towards VB on an extended decay curve which is characteristic of the semiconductive material of target 14. The next arrival of the beam at time t5 again charges area a0 to potential VC in accordance with the high level potential applied to area a1 at time t1. When the beam arrives again at area a0 shortly before time t6, the voltage level of signal S0 has again decayed towards potential VB.

It should be noted that in so decaying, the voltage level at area a0 has dropped below potential VB before the beam L1 again arrives at storage area a0. Thus, at this time since area a0 is already at the lower range of potential below VB the arriving electro-n beam is able by bombardment of the storage area to charge the storage area towards potential VK at time t6 in accordance with the low level of signal S1 at time t5.

llt is not necessary to consider signal SO in further detail since in explaining what occurs at time t2 through ts all separate cases of operation of the signal shifting apparatus of Fig. l have been clarified. For example, at time t3 a negative signal region was shifted into an area which had previously been charged to the lower potential range by a negative signal. At time t4 a positive signal region was shifted into an area which had previously been charged to the lower potential range. At time t5 a positive signal region was shifted into an area which had previously been charged to the upper range of potential and at time t6 a negative signal region was shifted into an area which had previously been maintained at the upper range of potential. Thus all separate cases of operation of the signal shifting apparatus of Fig. 1 have been explained in detail.

summarizing now the operation of the embodiment of the invention shown in Fig. l it should be clear that in operation the signal shifting apparatus receives binary intelligence signals applied to input terminal 1 and effectively shifts those binary signals over storage surface S to storage area a0 where the shifted or transported intelligence signals are coupled to output terminal O and thence to output conductor 13. Each signal so shifted is delayed by the .time required for the signal to progress from inputstorage area a1 to output storage area a0. The simple embodiment of the invention shown in Fig. 1 has a single electronbeam which by being cyclically deflected across storagefsurface S between areas a; and a picks up signals deposited at area aI and advances them to area aofor coupling to output-conductor'f13. `Either positive or negative signals may'be shifted across'the storage lsurface and therefore in 4operation the simple embodiment ofthe invention shown in Fig. l may function as Va l-binary digit shift register.

Summari'zing also thevarious characteristics which `are exhibited by the target electrode, itis clearY fromn the precedingV description that'the target electrode should be capable of exhibiting asecond'ary emission ratio greater than unity in order to provide either a positive, orl negative net current low to the area upon which the electron beam is impinging. Secondly, it is also 'clear from'the discussion set forth hereinabove that the matcrialfrom which the targetelectrode is formed should have a bulk resistivity which is sufficiently low to allow charge` remanents left by the moving electron beam todischarge to the conductivefbackingl of thettarget electrode;so., that the regions where the remanents were left is` discharged to a point below the crossover potential'Vr'before kthe succeeding sweep of the electron beam. Conversely, a third requirement of the target electrode is that it ,have a bulkvresistivity which is sufficiently high to .permit partial charge retention by the surface of the target during the flyback period of the electron beam, and in addition, to permit the use of an electron'beam of reasonable current density. In general any semiconductorwih -satisfy the foregoing criteria, since all known semiconductors will readily emit secondary electrons, .andhave a bulk resistivity which is sufficiently high to permita charge to be placed on the surface thereof while stilll being of sufficiently low resistivity to permit the charge to,leak off if left unsupported by a holding beam ofV electrons. It should benoted however,` that the selection of. aparticular semiconductor. material for the target electrode -will inliuence the maximum iteration yrate at which binary information in the form of charged areas can be stepped across thesurface of the target electrode, since=the2bulk resistivityfanddielectric constant of the materialwill determine the time constant of the discharge path for surface areas which have been left with a high level charge as the electronlbeam sweeps past. In other Words, the time constant of the selected material will influencethe time to be allotted for a sweep ofthe electron beam, since the time constant should be sui'iciently small relative to the period of the beam sweep to enable target 'areas having charge remanents left by the beam sweep to'discharge to a voltage below the cross-over voltage Vrbefore the electron beam again impinges on the area during the successive sweep. On the other hand, as will be understood in more detail from the description set forth hereinbelow, the time constant of the particular semiconductive material selected will also intiuence the flyback time of the electron beam since the time constant should be suliiciently'large relative to the iiybacletimeto prevent a charged area from discharging below the crossover voltage Vr duringthe yback period in which the holding beam is returned to its initial position to initiate another scan. Y

Typical materials which may be employed in the target electrode in practicing the present invention, are monatomic semiconductors such as silicon. and germanium,

semiconducting ceramics such as zirconium oxide,.me tallic oxidesemiconductors such-as copper oxide, or intermetailic compound semiconductors embodying elements of the third and fifth columns, for example, of the periodic table. Still other'rnaterials which may be employed in the target electrodeare Vthose materials, such as certain glasses, which become semiconducting when can be. shiftingthrough the-apparatus may be madevery 16 Y heated to'an elevated temperature. For example,',(orxr-k ing 0080 Lime glass exhibits a bulk resistivity-"of j.1'3j: megohm ,centimeter at 350 centigradeand.afdielectric constant of6.'75,.while VCorning `774 b,orosilicate, has al bulkV resistivity of 4 megohm centimeters at"v ,0 centigradeandhas a dielectric constant ofSJQrlaccor'd, ingly, eithenf-these.materials could`be employecl'in practicing -.the invention. To illustrateithis'latterpoint further, the foregoing figures for b'orosilicate,.glasslindi cate 'that'the glass has a timelconstant, of,.,approxmately 1.75 10-6 seconds at -350.centigra'de.t `1Thus fif .onlegas sumes a ratio -offbeam sweep interval'to yback interval A ofiive to one, it will beseen that thisparticular material: WilLOperate, veryjeffectively atY iteration rates f off'thev 2 ordergof 200 kilocycles since the` vtime'constant'.'of/the` targetelectrode will then be approximately twice as. long as the'flyback interval and will beless ,thanhalf as'long as the beam sweep interval. Accordingly,.ifthe-,tube4` operating voltages '.are selected to proyidea crossover voltageVr which is substantially` less-than. Athe voltage' Yto which a .chargedlarea of the.target ldischarges .during the liyback interval, and `morelthany the voltage. towhich a Vcharged tarea` discharges. during a sweeplfin'tervalg'the target. of boro'silicate fglass .will function in laccordance' with. the teachings of.` the invention.

lIf the general configuration shown iny Fig. 1 is provided as :a .multiple array .wherein a Vplurality of electronY beams are vproduced,.arrangements may be made, in which aA signal advanced by one beam is pickedup'by asuoces-Y t siveV beamand. advancedfstill further, the'binary` signals 1 therefore seriallyY progressing from each beam tothe suc-v. cessive beaml ateach cycle of the deflection ,voltagegln x a multiple array of thistypethenum-ber of.signals which large if desired. Such a multiple-beamshifting apparatus,l i is shown in Fig. 4. i Y

In the multiple beam embodiment of ythe` present l.ing vention -shown'infFig `4, a common .cathode K supplies Y, electrons toy produce five electron beams (L1,L2,.L3;:L4l and L5) .through a perforated accelerating anode These beams pass'through .anarray' of alternatelyconf nected deecting-pla-tes'Dl and D2 and arethereby sweptback andforthjin synchronism by a sawtooth ,.deiiection voltages'upplied tothe deflecting plates -r bygthesource ofdeiiectionsignals 16. It will be .understood that .a1lj the deection platesDl are connected to'the sourceof deflection signals 16' and'that iallfthe deflectionplates D2 are connected. togetherand separately--connectedt the source of vdeliectionsignals16.

In Fig. 4 the electronA beams L1 through L =,ar;e ..shownv as kthey would appear at the completion ofvtheir return sweep or flyback, electron beam L1;then being directedatV storage area a1 and electron beam-L5 beingdir'ectedafa storage area of surface S-just preceding the,storage:areaV a0. YThe-amplitude of motion of-eachrbeamV Aacrossrthe storage surfaceS is equal tothe v spacing ofthe beams -at the storage -surface and therefore when storage areaY (1f Y is charged toits -upper range of potentialk by a positive signal the next .forward sweep of beam L1 willadvance orlshift thepositive signal to a point where it -canvbe in -efectV picked -vup by beam L2, the positive Vlsignalj progressing in this-#manner from beam. to beam at 4each, cycle ofthe deflection voltage until at the endof'theSth .Cycle the charged area is shifted by'beam L5 to ,theoutput storage areavao. While `this tirst binary-intelligence signal isbeing vshifted, to output storage -areayy aoothe'r intelligencesignals may 'be lserially `applied to Yinput ,te,rminal Iso Vthat `a serial train of intelligence signalsfis produced which are being synchronously shiftedortransported across vstorage surface S. It Vwill bellvllderstood therefore that the particular embodiment oftheinvention' shown in Fig. 4 is adapted for the shiftingj and rstorageof five binary .intelligence signals. e Y

f The particular, embodiment of. .the invention showniin t Fig. has a limitation which may Vlimit the use'ful"life time of the apparatus in that the storage surface S is exposed to or has a line of sight view of cathode K so that negative ions and particles of cathode material emitted by cathode K may be accelerated against storage surface S where they may have a deleterious effect on the secondary emissive properties of the storage surface. Furthermore a somewhat complicated mechanical structure is required for positioning the deflection plates D1 and D2 so that symmetricalV electrostatic deflecting forces are applied to all of the electron beams L1 through L5.

The described disadvantages of the particular embodiment of the invention shown in Fig. 4 are eliminated in a preferred embodiment of the invention shown in Fig. 5, in which magnetic deflection is utilized for the deection of the multiple electron beams which are formed in the signal shifting apparatus. As shown in Fig. 5 cathode K has an extended cylindrical shape and is enclosed by coaxial cylindrical grid G. Collector anode C is composed of a large number of conducting vanes which are coaxially arranged around cathode K to form a generally cylindrical structure in which the vanes are arranged slantwise as in a Venetian blind to form a large number of angled openings through which electrons emitted by cathode K pass to form multiple electron beams. All the vanes of collector C are positioned and conductively connected to one another by an annular aligning ring 24.

Semiconductive target 14 is cylindrical in shape and coaxially encloses the cylindrical structure of anode C. As shown in Fig. 5 portions of target 14 are cut away to allow an unobstructed view of the interior structure of the signal shifting apparatus. C are so angled that no area of storage surface S of target 14 has a straight line of sight view of cathode K. An axial magnetic field is provided by a magnet winding M which encloses the evacuated tube E.

The applied axial magnetic eld causes electrons emitted by cathode K to travel in arcuate paths thereby causing the electrons to 'avoid the barrier presented by the vanes of collector C. Because of their path curvatures, emitted electrons can pass between the angled vanes of collector C to thereby form arcuate electron beams of rectangular cross section which may impinge upon storage surface S. To such electron beams L1 and L16 are shown in Fig. 5. It will be understood howeverV that every aperture of collector C is capable of producing an electron beam.

As shown in Fig. 6 the outer surface of target 14 is conductively coated to form backing plate B. Output terminal O is an isolated vertical strip of conductive material also plated on the outer surface of target 14 opposite storage area a to which beam L16 may be deflected in the operation of the signal shifting apparatus. Input terminal I as shown in Fig. is a vertical conductive strip which is coated on storage surface S of target 14 at a point where it may be bombarded by electron beam L1 during the operation of the signal shifting apparatus.

It is clear from a consideration of the structure shown in Fig. 5 that ions and uncharged material emitted by cathode K will be unable to reach storage surface S. The uncharged particles will of course travel in straight lines and will therefore inevitably be intercepted by the vanes of collector C while charged particles since their mass is far greater than the mass of electrons will not have sufficient path curvature to pass through the angled vanes of collector C and will therefore also be intercepted by collector C.

The operation of the signal shifting apparatus shown in Fig. 5 may be more readily understood by referring to Fig. 6 in which lthe signal shifting apparatus is shown as it would appear when viewed from a point directly above cathode K. Annular ring 24 is not shown in this view for the purpose of facilitating examination of the angled vane structure'of collector C and of the electron beams which are formed by passage of electrons through the apertures The vanes of collector 18 of collector C. In Fig. 6, 16 electron beams L1 through L16 are shown of a total of 48 electron beams which may be formed by collector C.

It is clear that if the applied axial magnetic field is varied between upper and lower values each of these beams will correspondingly be varied in curvature. A! the lower value of iield strength, the curvature of each beam will be relatively slight although suiiicient to allow the beam to pass through the angled vanes of collector C. As the applied field is increased to its upper value the curvature of each beam will be increased so that the point of impingement of each beam is advanced from` the storage area at which it is normally directed (at the lower value of the applied magnetic field) to an adjacent storage area.

In Fig. 6 all of the beams L1 through L18 are shown as they would appear when the applied magnetic field is at its lower value, beam L1, for example, being directed at storage area a1 and beam L15 being directed at a storage area immediately preceding storage area a0. When the axial magnetic eld is raised to its upper value beam L1 will change its curvature until it assumes the path indicated by dotted line 20. Similarly beam L2 will change its curvature until it assumes the path indicated by a dotted line 25 and beam L16 will assume the curvature indicated by a dotted line 26 so as to impinge upon storage area ao.

In operation source of deection signal 16 cyclically varies the current applied to winding M so as to cyclically vary the magnetic field between its lower and upper values. In response to the varying magnetic field, the electron beams L1 through L16 are swept back and forth in synchronism, each increase of the magnetic field to its upper value causing an advancing sweep of' the beams and each decrease in the magnetic held to its lower value causing a return sweep of the beams. Since the amplitude of motion of each beam is equal to the spacing of beams it is clear that an intelligence signal introduced at terminal I may be shifted from beam to beam in the same manner as has been described in connection with the multiple beam shifting apparatus shown in Fig. 4.

In the preferred embodiment of the invention shown in Fig. 6 output terminal 0 has been separated from input terminal I by a distance which allows the signal shifting apparatus to be used as a 16 digit shift register in which 16 binary intelligence signals may be stored on storage surface S as the intelligence signals are shifted from storage area a1 to storage area no. It is clear, however, that by increasing the spacing between output terminal O and input terminal I the capacity of the shift register may be greatly increased. For example, by placing output terminal O opposite the storage area which immediately precedes storage area a1 a shift register having a capacity of 47 binary digits may be obtained.

Moreover the digit storing capacity of the preferred embodiment of the invention shown in Fig. 6 may be additionally increased by many orders of magnitude by substituting for target 14 a modified target 14a of the general type shown in Fig. 7a. As shown in. Fig. 7a, a helical conductive stripe J is established on storage surface S, helical stripe I starting shortly above terminal I and winding round and round storage surface S and ending below output terminal O. The successive turns of the helical stripe I dene or demark boundaries for a long helical track 31 on storage surface S, track 31 being always bounded above and below by upper and lower turns of conductive stripe l, so that track 31 winds round and round storage surface S from input terminal I to outputterrninal O.

As shown in Fig. 7a, input terminal I may lbe a square or area of metal iilm deposited on storage surface S at the beginning `of track 31 and electrically connected to input conductor 12 which may extend to terminal I through a small hole in target 14a. Output terminal 13 as shown in Fig. 7a, may be an isolated conductively aeeogaea tioned at the en'dof spiral track 31. Y

,The helical conductive stripe J is provided to Vcause successive turns' of track31 to be electrically isolated from one another so that intelligence signals which may be shiftedl along on one turn of track 31 cannot propogateacross `stripe J into adjacent turns. To insure such isolation, conductive stripe l may be kconnected to a source 'of relatively low potential VJ. It will be understood lthat potential V11 is in the lower range of potential, that is, that potential VJ is lower than potential VR mentioned `hereinbefore in connection with the description of Fig; 2. Y

iConsider, for purposes of example, how the 'operation o f the signal shifting apparatus shown in Fig. 6 would stitutedfor 'target 14. L'et it be assumed that target 14a would"'befs'ooriented that electron' beam L1V impin'ged upon terminal I-"of target' 14a whileA electron beam L3 imi' gedup'on'an areaofstorage surface S immediately above 4output terminal jO,

In order 'toi facilitate description of the operation 'of the signal shifting apparatus under these vstated conditions there is shown' in Fig. 7b a development of target 14a showing 'storage surface S as it would appear if target 14a W'ere'cut away along a dottedline 30 (shown in Fig. 7a) and then unrolled to expose storage surface S as a atarea. y

As 'shown in Fig. 7b'spiral track 31 has live turns about storage surface S, these turns being designated turn 1, turn 2,' Vturn' 3, turn 4 ,and turn 5. In addition for the purpose efindicating the normal areas of impingement of electron beams L1, L2, L3, to L48 (where L48 is the fortyeighth' beam"forrned by collector C), these areas of imping'e'nient of the beams 'are designed P1, P2, P3, etc. to P48' and are demarked by dotted lines as shown in Fig. 7b.

It will be'understood that 'the "areas P1 to P4s'correspond 1to` the areas of im'pinger'n'entfof the electron beams L1 'to Lv'vvhen the applied magneticfield'is at its lower value. Inoper'a'tion when the lapplied magnetic eld is being varied'bet'ween its upper and lower values, beam L1, orexainple; 'will move back and forth between areas P1 and Pg, each 'of fthe otherl beams similarly moving between its lassociati'ed area and the next successive area.

Fory purposes of 'clarification many ofthe areasy of projectionfhave not been shown..-It will be understood,

evertliat they are uniformly distributed across lstor- 'siirfacef S. Thereference 'character Pn is used to d ignat'e `rthe impingeinent' area immediately preceding t ning line orcutaway lline 30 while reference a P7111, PM2 have been utilized for designating the `two `ji'n'pfingeinent areas immediately succeeding sectior'1ir'1g'line"30.V In addition a'dotted line -32 designates the, projected boundary of output terminal O on storage surface Sand-adotted line 33 designates the projected boundary of backing plate B on'storage surface'S.

' "Considernow with lreference to Fig. 7b the operation of th'e'n'i'did signal shifting apparatus. If an intelligence lsign'al is applied to input terminal I, the next forward svvee'p',of vvthefelectron beams'will advance the applie'dj intelligence signal from input terminal I to that portion, Iof areaY `P2 -which liest within turn 1, this area being 'designatedr for purposes of convenience P2 1. OtherY areas of track 31 will be similarly designated. It will be understood, of cburse,`th`at'lthe intelligence signal isfso' advanced'. by beam L1 sweeping across surface S v the shifted'intelligence signal may be increased `andfin from area1P1 to area P2. IBecause ofthe isolating action of' con'ductive'stripe I when it is maintained at potential VJ, theintelligence signal can -only propagate in the described-manner (from larea `P1 1 to area vP2 1) and canno 'piropagat'el across conductive stripe. I to areas P 1 1"j'or 'P2 2. Thus, infth'is manner --the influence ofV a charged area on one/turn of track 31fis entirely isolated from adjacent turns.

v`Itis clear therefore that while beam L1 is shifting an 7 5 to produce a serial train'of intelligence signals which are intelligence signal froin P1 -1-to P1 1itmayal'seb I ing asecondintelligencelsignal fromvP1 2ft "P272, M intelligence signal fromtP1 3 tofP2 3,'-a"ifourth inte gencc lsignal lfrom P1 ;{"ito; P2 4,`jand a fifthintellig` signal from`P1 5"to P215. lThus, by 'reason "ofthe ing action of conductive stripe I, beam` L1jnray'simul neously advance tive independent intelligence 'sgnals"` n the tive turns of spiral track J. Each ofthe other be is similarly operable for shifting intelligence signals o each of the live turns of track 31. ,a

In the light of the foregoing explanation "consid therefore the path followed by an intelligence Vsignal4 troduced at input terminal I. As `stated"hereinbeforf K the irst advancing sweep of electron beams-L1 through L48, the signal is advanced by beam L1 "from`fP1 -1 P2 1. At the second advancing "sweepV ofthe" electron` beams 'the signal would again be 'advanced' along turn to area P3 1. In this manner the signal progresses' tio' beam to beam along turn 1, proceeding from turl '1L turn'2 by being 'shifted' yfrom P(,) 1 lto 'P(+1). 2 'a progressing in like manner along turn 2 until it progresse from'turn 2 to turn 3 by beingshifted from area P0154 to area P(+1) 3. The intelligence signal progresses serially in this manner vfrom beam to beam along successive turns Vof track 31 until itV arrives at the ticular vareavvh'ich Vis stationedl opposite output terminal O, vthis varea as shown in Fig. 7b being designated as'area P3 5. The intelligence signal then capacitative'ly'l-pr duces an output signal at terminal O which is applied to output conductor 13. f

' It will' be understood that as the first lapplied Yintelligence signal is progressing along spiral track31 another intelligence signal may" be applied "to input terminal I simultaneously being shifted from input VVterrilinalfl to output terminal O. The digit storage and shifting capc ity of the preferred embodiment of the invention thereby increased, from a 47 digit capacity (with "targ 14) to a 194 digit capacity with the modified tai'getla shown in Figs. 7b and'7b. Storage capacities ofi-thoM` sands of binary digits may be readily attained infth manner on a storage surface of relatively smallar'ea. 1 'i The storage capacity of surface S is much. enhanced by the fact that individual storage areas need' not beanyi larger than is required for propagation of an 'intelligencesignal from the storage area to an adjacentarea. Thus track`3'1'may be made as narrow as will permita-propagationv'of signals along the track. .The energy contentar effect amplified by widening thelast4 turn, tuifn 5, of track 31 as it approaches output terminaLO so .that-thearea v uscd 'for the propagation of intelligence signals increascSL-Jy as the output terminal is approached. Intliis mannerY the intelligence signals arriving at-theoutput area P3515 have sufncient energy content to produce a usable output signal while intelligence signals propagating in precedingturns in track 31 may have very low energyv contents.

Although the use of helical striping of storage surface' S in the manner generallyl described in connection with Figs.` 7a and 7b is a preferredmethodfor increasing-the; 1. storage capacity of the signal .shifting apparatusy ot thef'"` presentinvention, similar results may be obtainedfwith"V j'` an unstriped target structure by using a modified collector C1 of a type shown in Fig. 8. As shown in Fig. 8 zol-v lector C1 has a large number of apertures which are hclij cally arranged about collector C1 so that a helicalarray` of electron beams maybe formed by electrons passing through these apertures. In operation intelligencesig'# nals applied to input terminal VI will be serially vshifted in v a helical path or track von surface S from input terminal I to output terminal 0,'a progressing intelligence signal being shifted from beam to beam of the helical array of beams during the course of its passage. y V.It shouldbe understood, of course, vthat theforegoing* disclosure relates only to preferred embodiments of the invention and that numerous modifications or alterations may be made therein without departing from the spirit and scope of the invention. For example, in the several embodiments of the invention which have been described hereinbefore binary intelligence signals have been stored on a storage surface by being applied to an input terminal which is in direct electrical contact with an input 'area of the storage surface. However, it is clear that direct electrical connection between the input terminal and the input storage area is not required and that other forms of coupling of the intelligence signals to the input storage area may be utilized. Thus in some embodiments of the invention the input terminal may be a conductive strip established on the back surface of the target electrode opposite the input storage .area` so that binary in` telligence signals Which are applied to the input terminal are capacitatively presented at the input storage area. In other embodiments of the invention, the electrical input intelligence signals may be utilized to control the passage or interruption of a separate writing beam which is permanently directed at the input storage area, the writing beam then successively charging the input area to its upper potential range or leaving the input area at its lower potential range in accordance with the successive voltage levels of the input signal.

It will also be clear to those skilled in the art, that the application of the basic principles of the present invention permit bidirectional transport or shifting of bilevel electrical signals across a storage surface as Well as unidirectional transport of signals in the manner hereinbefore described. In the several embodiments of the invention hereinbefore described, reversal of the signal shifting direction may be readily accomplished by reversing the velocities of sweep of the electron beams so that the beams have a sufficiently low velocity in the desired shifting direction and a higher velocity in the undesired shift direction.

Inthis manner reversal of shift direction may be obtained whenever such reversal is desired. Moreover the signals may be shifted forward and backward at varying speeds through corresponding variation of the beam sweep velocities and may even be heldstationary for indefinite periods by halting the cyclical deliections of the electron beams. With such modes of operation, the signal shifting apparatus of the present invention is ideally adapted for use as a variable speed buffer or intermediate storage device. l

Still other substitutions, additions and alteratio-ns to the present inventio-n may be practiced by those skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.

What is claimed as new is:

1. In the process of shifting stored bilevel electrical signals across a secondary electron emissive surface of a semiconductive target electrode on which the bilevel signals are stored as the voltage levels of surface regions each charged to an upper or lower range of potential, the method of shifting a first bilevel signal from a first region to an adjacent second region which comprises the steps of: directing a first electron beam at the first region to maintain the first region at its potential range so long as the -beam impinges upon the first region, and deflecting the first electron beam across the surface from the first region to the second region at a sufficiently low velocity to maintain the surface region beneath the moving beam at the potential range of the first region thereby to shift the first signal from the first region to the second region with the first electron beam.

2. The method defined by claim 1 which includes the additional step of removing charge from the surface to tend to discharge each surface region to the lower range of potential whereby the first signal as it is shifted by .the first electron beam is confined to the surface region beneath the beam and does not leave remanent signal trailing behind. I

3. The method defined by claim 2 which includes the further step of redeflecting the first electron beam from the second region to the first region at a velocity suiciently high to prevent shifting of signals from said second region to said first region by said beam, whereby the beam may be utilized for unidirectionally shifting an additional signal from the first region to the second region.

4. The method defined by claim 2 which includes the additional step of Shifting the first signal from the second region to a third region 4by directing a second electron beam at the second region and deflecting the second electron beam across the surface from the second region to the third region at a sufiiciently low velocity to maintain the surface region beneath said second beam `at the potential range ofl said second region.

5. In the process of shifting stored bilevel electrical signals across a secondary electron emissive surface of a semiconductive target electrode on which the bilevel signals are stored vas the voltage levels of surface regions Y each charged to an upper or lower range of potential, the method of unidirectionally shifting bilevel signals across the surface from a first area to an adjacent second area which comprises cyclically performing the steps of: deflecting an electron beam across'the surface fro-m the first area to the second area at a predetermined velocity such vthat as the beam is moved across the surface the surface region beneath the moving beam is maintained at the potential range of the first area to thereby shift a signal from the'first area to the second area, and redeflecting the electron beam across the surface from the second area to the first area at a higher velocity such that the shifted signal is not shifted back to the first area but is left at the second area to which it has been advanced.

6. In the process of shifting binary electrical intelligence signals across a secondary electron cmissive storage surface of a semiconductive target electrode from which charge is being removed so that areas of the storage surface when charged to an upper-range of potential will be rapidly discharged to a lower range of potential thereby tending to maintain the storage surface at the lower range of potential,` the method of charging a predetermined area of the storage surface to the upper range of potential whenever an adjacent area of the storage surface is at the upper range of potential, said method comprising the steps of directing a beam of electrons at the adjacent area to maintain the adjacent area at the upper range of potential so long as the electron beam impinges upon the adjacent area, and deflecting the electron beam across the storage surface from the adjacent area to the predetermined area at a sufiiciently low velocity to maintain the region of the storage surface beneath the beam at the upper range of potential.

7. In the process of shifting binary electrical intelligence signals across a secondarily emissive storage surface of a semiconductive target electrode from which charge is being removed so that areas of the storage surface when charged to an upper range of potential will be rapidly discharged to a lower range of potential thereby tending to maintain the storage surface at the lower range of potential, the method of charging a predetermined area of the storage surface to the upper range of potential whenever an adjacent area of the storage surface is at the upper range of potential, said method comprising the steps of directing the beam of electrons at the adjacent area to eject secondary electrons from the adjacent area and increase the potential of the adjacent areafor expanding at a predetermined initial velocity the boundaries of the surface region at the upper range of potential,

and deflecting the electron beam across the storage surface from the adjacent area to the predetermined area at a velocity less than or equal to the predetermined initial velocity to maintain the region of the storage surface beneath the beam at the upper range of potential.

asejasa" l r`23 Y *8. A csignalshiftingV apparatus comprising aiseinic'onductive target electrode having a secondary'electiorierni'ssive ls`urface,lmeans for *successively"storing'applied bilevel electrical intelligence signals on a predetermined initial area of said surface, means for shiftingstored signals acrosssaidsurfa'ce from the' initial area toY a remote area of said 'surface,'and' an output electrode electrically coupled vvto' the v*remote area whereby bilevel elec tr-icalfsignals shifted across said 'surface-tofthe'remote area '1a-re presented as corresponding 'bilevelz potential variations at' said outputfelectrodeY 9.- The signal shifting' apparatusdefined by claim 8, wherein said" means 'forshifting "stored lsignals-'across saidr surface includes beam forrningf apparatus for forming' VYa first electron "flrolding beam'and' dire'ctingf'said "iloid-v ing-beam ats'aidIinit-ial area 'to regenerate binary electrical intelligence signals stored 'on the -initial area, and b'eam defiection apparatus Yfor'- successively deflecting said first holding bearnbaclcu and Yforth across said vsurface between 'the initial area andan adjacentarea fof' saidvv surface, the-beam being deected'fforwar'd' 'across' s'aid said initial area are-successively shifted across said surface beneath thefmovingbeam to the adjacent area.

10. The signal `shifting 'apparatus defined/by claim wherein said beam forming apparatus includes means 'for forming a secondvelec'tron holding beam and for directing said second electron beam/at the adjacent area to regeneratefsignals shifted tothe adjacent area by the first electron beam, and said beam deecting apparatus is operable for successively deflecting said second' electron beamfback and forth-across said surface between the adjacent area and a further adjacent area, the second beam 'being deflected forward across Vsaid surface from the adjacent area to the further adjacent area at a velocity. such that during successive forward deflections of the second beam; signals successively regenerated bysaid srecondbeam at the adjajcentlarea are successively shifted across said-surface beneath themoving beam tor the yfurther adjacent area.

11.'The signal shifting apparatus defined by claim- 8 wherein said surface has a plurality of sequentially -adjacent storage means established thereonfs'aid plurality of areas including the initial area-and an areaadjacent to L and sequentially preceding theremote area, and-said meansV for shifting: stored signalslfrom the linitialarea to the remote area includesf-apparatus'for `forming a corresponding `plurality` of.A electron ffholding beams and for directing s'aid beams at'correspondingly associated storage areas 'respectively of said plurality of areas, and beam fde'ecti'onfapparatusYfor cyel-ically deflectin'g said beams back and'iolrth4 across-said sur-face in synchronism each beam beingfdeectedback -andfforthf'between its respectively associated kstorage areaand-acorresponding sequentially adjacent area, -each b eam-being-deected forward across said surface-at a sufficiently low velocity to shift Signals-stored atthe associated area-across the 'surface to La sequentially adjacent area, whereby signals originally stored at Atheinitial area varel-shi-ftedacross ythe'surface to a sequentially adjacent areaatveach-cycle of'fdeflection of the" beams, v stored signals progressing in |this manner from area to area untilthey-are shifted to-the remote area;

l12. Azsignalshifting apparatus comprisinganevacuated y container, -.a semiconductivetar-get electrode positioned Within-said ycontainer and havingva :secondary electron--emissive surface, first-means 4responsive `toan applied", binary -electrical signalfor selectively charging an initial arcaof said surface toan upperor-lower range of potentiallin--accordance withthe-binary-signal, second means for. rforrning an` .electron --holdingl beam-andfor directing said `beam at the initialA area .to Vbernhard theinitial area with electrons to maintain` the initial area at i area when it is ythe rst range' of potential to imaintaim the potential range whichl'it had immediately'before bom- 75 `wherein said apparatus includes fourth means `for remov- VVtaf-said surface can only remain charged to the-upper tial, means for removing charge from said storage surface `to tendto maintain said storage surface at a predete Z4 Y .l ba'rdment'by said beam, and'thirdjmeans'for' defl'ee'tir* said electron beam acros'ss'aid surfacef'away from'tl'a initial area at'a velocity suchasfto maintain the 'regi` ofsa'id' surface beneath the beam at the same potenti range as the potential range of the initial area frornfwhiV the Vbeam started its sweep. `f t1'3. The signal shifting apparatus defined b'ynclaim'l wherein said apparatus includes fourth meansffor rem` ing charge from said storage surface to''tendto"n'iaintan'g` sai-d surface at one of said upper and lower franges" potential, whereby areas of said 'surfacecanonlyrem *n charged to lthe other Vof's'aid ranges of potentialv are being bombarded by electrons of the holdin`g\beat1r so that areas yleft `behind the moving electron beam rapi tischarge'to "s'aid'one'ran'ge of potential.V Y i f l4. The signalI vshifting apparatus defined' -by`\"c`laimi 153 wherein said-'third meansincludes apparatus for' rede'e, ing said electronbeam back across/said surface in@ returnsweep to the initialarea at 'a1 -velo'cityV `greateE than the'fi'rst-named velocity, such that as the electro beam sweeps across said surface the beam supplies insu cient electrons to appreciably charge'or discll'argeis` surface, whereby areas of said surface traversedl by sar beam on its return sweep remainiat said ,one range potential. l

15. The signal shifting apparatus definedby efraim-31;`

ing charge from said storage surface toV tend to mintilf i said surface at the lower range'oflpotential wherebyfares range of potential if they are being bombarded by: ele trons of the holding beam, so that areas left behindV the moving electron beam rapidly discharge to thellower range of potential. t, 16. The signal shifting apparatus defined by claim-913 wherein said Vfourth means includes apparatus for red flecting said electron beam lback across said -surface'in'l` Y return sweep to the initial area at a second velocity? greater than the first-named velocity such that `as the electron `beam sweeps across said surface, 'the-bea supplies insufficient electrons to appreciably charge f discharge said surface whereby areas of said surface? traversed by said beam'on its return sweep remainfat the lower range of potential. Y'

17. An evacuated electron discharge device including charge storage surface having first-and second adjacent* storage areas, charging means operable for chargingsai first storage area to a predeterminedfirst range of poten mined second range of potential, beamA` forming inea for forming an electronV beam'andv fornormally'direc x ing said beam-at said first storage area-to engage said first area when -it is at the first range ofpotential toi maintain the rst area at the first range of potentil,- and deflection apparatusactuable for deecting said `bea to said second storage area to lcharge said second storage, area to the range ofpotential previously maintained at- Y said first storage area. 18. An evacuated electrondischarge devicel including a charge storage surface having first, secondamd thirdV sequentially adjacent storage areas,'charging means 'oper able for charging'sadvfirst storage area4 to a predcter" l mined-first range of potential, means for removing chargel from said storage surface to tend to maintainrsaid storage` surface at a predetermined' second range of 'potentia'l,f5 beam forming means `for-forming first and secondcl'ec# tron beams associated with said first and second storage`Y areas respectively and for normally directing each bearn"v at its associated storage area to engage the associated the associated areal at'thefvrstrange ofpotential, a-nd deflection apparatus actuable fondeecting said. first and second beams to said second --and third `storagefareas` respectively, to charge said second and third storage area second,

to the potential ranges previously maintained at said irst and second storage areas, respectively.

19. An evacuated electron. discharge device including a charge storage surface having a series of first, second, nth, n-l-lst storage areas, means operable for charging said first storage area to a predetermined first range of potential, means for removing charge from said storage surface to tend to maintain said storage surface at a predetermined second range of potential, beam forming means for forming first, second, nth electron beams associated respectively with correspondingly numbered storage areas and for normally directing each beam at its associated storage area to engage those areas which are at the first range of potential, and deflection apparatus actuable for deliecting said iirst, nth electron beams to said second, third,

n-l-lst storage areas respectively to charge each of the storage areas to the potential range previously maintained at the immediately preceding storage area in said series of storage areas.

20. In a signal shifting apparatus in which an extended electron holding beam is deected across a secondary emissive storage surface to shift bilevel electrical signals across the surface beneath the moving beam, apparatus for electrically isolating predetermined levels of the e storage surface corresponding to associated levels of the extended electron beam so that independent bilevel electrical signals can be shifted across the surface at each of the predetermined levels by the electron beam, said apparatus comprising: conductive striping established on the storage surface and demarking the predetermined levels of the storage surface, and means for maintaining said conductive striping at a predetermined potential such that bilevel electrical signals being shifted across the surface at the predetermined levels cannot propagate across said striping to adjacent levels.

21. In a signal shifting apparatus in which a plurality of extended electron beams are deflected across an inner secondary emissive storage surface of a generally cylindrical target electrode to shift bilevel electrical signals across the surface beneath the moving beams, apparatus for electrically isolating levels of the storage surface to form a long helical track of unobstructed storage surface along which bilevel signals can be shifted by the beams, said apparatus comprising: a helical conductive stripe established on the storage surface, said helical stripe having a plurality of successive turns winding around the storage surface, the successive turns of said conductive stripe defining boundaries for the helical track, and means for maintaining said stripe at a predetermined potential vsuch that bilevel electrical signals being shifted across the surface on the helical track cannot propagate across the bounding turns of said helical stripe.

22. A signal shifting apparatus comprising an evacuated envelope, an electron emissive cathode centrally positioned within said evacuated envelope, a generally cylindrical semiconductive target electrode surrounding said cathode, said target electrode having ar1 inner secondary electron emissive storage surface, a generally cylindrical collector electrode surrounding said cathode and positioned intermediate said cathode and said target electrode, said collector electrode having a plurality of axially extended apertures for forming a corresponding plurality of spaced axially extended electron beams directed at said storage surface of said target electrode, deflection apparatus for generating an axial magnetic field and for cyclically varying said field between upper and lower values so as to correspondingly increase and decrease curvature of the electron beams to sweep the beams back and forth across said storage surface, the plurality of beams being directed at a corresponding plurality respectively of spaced sequentially adjacent axially extended areas of said storage surface when the eld is at its lower value, the amplitude of motion of each beam across said surface being equal to the spacing between said areas, iirst means for normally maintaining said target electrode at a predetermined first potential with respect to said cathode such that the secondary emission ratio of said surface is normally less than 1 when it is bombarded by electrons in said electron beams, second means for storing applied bilevel electrical signals on a region of said storage surface in a predetermined one of said plurality of areas, said second means including apparatus for charging the region whenever the applied bilevel signal is at a predetermined level, to a predetermined second potential such that the region has a secondary emission ratio greater than 1 when it is bombarded by electrons in said electron beams; whereby after storage of a bilevel signal on said region, each cycle of deliection of said beams causes the stored signal to be shifted to a sequentially successive area of said plurality of areas.

References Cited in the le of this patent UNITED STATES PATENTS 2,560,585 McMillan July 17, 1951 2,598,919 Jensen June 3, 1952 2,600,373 Moore June 10, 1952 2,684,449 Rich et al. July 20, 1954 2,704,336 Kazan Mar. 15, 1955 OTHER REFERENCES Storage Tubes and Their Basic Principles, by M. Knoll and B. Kazan, pp. 89-92, published in 1952 by John Wiley & Sons, Inc., N. Y. 

